New Battery cured Stop Start.

[geoffus]

The original battery on my E250 was dated 2014 and began struggling recently to start he car. The stop start function had also stopped working so main battery looked suspect.
Just had a new battery arrive and promptly fitted it. Stop Start is now back to fully working and the Eco button goes green as soon as the car is turned on and before even started.

If anyone is interested this is what the job entails.




New AGM battery from Ebay £118 with nextday delivery.
Exide AGM battery,





Place bonnet in service position and remove battery cover.



If you haven't done this before, just remove the links on the bonnet hinges.




To keep all settings while the main battery was disconnected I connected a spare 12v battery across the jump terminals, probably unnecessary to be fair.




The new battery case is almost identical to the original Varta.





The battery is secured with a clamp on the left of the battery by a 13mm bolt.
The battery terminals are 10mm bolts.




Remember to refit the breather pipe.




Even after a trickle charge overnight the original battery was only 12.32 volts.




After fitting straight out of the box, the new one was 12.67 volts.



Now with just ignition turned on the ECO button goes straight to green.
Car spins over now very fast and the temperature is around -1c at the moment.
So even with a slight variation of voltage, in my case 0.35 volts, was enough to stop the Stop/ Start from working.

 

[wongl]

Well done - it must be very satisfying getting your car back to full factory standard!

 

[Justintyme]

The original battery on my E250 was dated 2014 and began struggling recently to start he car. The stop start function had also stopped working so main battery looked suspect.
Just had a new battery arrive and promptly fitted it. Stop Start is now back to fully working and the Eco button goes green as soon as the car is turned on and before even started.

If anyone is interested this is what the job entails.


View attachment 106783

New AGM battery from Ebay £118 with nextday delivery.
Exide AGM battery,



View attachment 106785

Place bonnet in service position and remove battery cover.

View attachment 106786

If you haven't done this before, just remove the links on the bonnet hinges.


View attachment 106787

To keep all settings while the main battery was disconnected I connected a spare 12v battery across the jump terminals, probably unnecessary to be fair.


View attachment 106792

The new battery case is almost identical to the original Varta.



View attachment 106790

The battery is secured with a clamp on the left of the battery by a 13mm bolt.
The battery terminals are 10mm bolts.


View attachment 106793

Remember to refit the breather pipe.


View attachment 106794

Even after a trickle charge overnight the original battery was only 12.32 volts.


View attachment 106795

After fitting straight out of the box, the new one was 12.67 volts.

View attachment 106796

Now with just ignition turned on the ECO button goes straight to green.
Car spins over now very fast and the temperature is around -1c at the moment.
So even with a slight variation of voltage, in my case 0.35 volts, was enough to stop the Stop/ Start from working.

Yes, I'd say thats the cause of the erratic ECO behaviour in mine too, as the Aux battery has already been replaced.

 

[Atavus]

That slight change of voltage is the difference between good and duff. 12.7 is about the top end of charged and 12.3 is a battery that might not recover after a charge. It’s just a very small range and is a lot less than you’d expect.

 

[Gazwould]

I don't know how my 2011 original is still going as I have seen as low as 11.7V on the Maypole display as I initially connect .

Charged the display is just 12.1V !

Speed of cranking is fine .

Just dapped it on for the day and was 11.8V.

Nice write up Geoff , you've an OM651 and the battery is a 115 AGM ?

Would a charger surfice on the jumping posts instead of a 12V ?


Not sure why quite a band of people want the start strain working when the independents have condemned it .

 

[Gazwould]

Just took it off and fully charged @ 12.0V !!




Heavens knows how it's still going , must be because it's a deep cycle AGM and not lead acid .

 

[190]

12.0 volts just off charge is on the face of it terrible.

The problem is you can only get a sensible and useful state of charge voltage reading when the battery is rested and under no load. With modern cars the no load criteria is hard to determine without disconnecting the battery. A fully charged AGM should then be more like 12.9 volts and a non AGM 12.7 volts.

It would have been interesting to know what that new out of the box AGM was before it was fitted as 12.67 volts is not fully charged even if it did fix the stop start.

 

[Muckypaps]

I've just changed my main battery, and it didn't lose any settings except the clock, which updated itself after 5 second with ignition on.

 

[geoffus]

Just took it off and fully charged @ 12.0V !!

View attachment 106853


Heavens knows how it's still going , must be because it's a deep cycle AGM and not lead acid .

The original battery was a Varta AGM, it really only started to struggle these last few weeks going down to 11.7 volts a few days after an overnight smart charging, just before it was changed it was starting perfectly at 12.3 volts. I was not worried about the stop/start as I would always turn it off, but it was a good indicator of battery charge.
At the moment the car is not used very often and I have a tracker so it may be slowly discharging or perhaps the cold was enough to show the battery failing.

The wife's car is still on its original 8 year old battery and starts as new !

Yes mine is the OM651 and the battery is the 115 AGM version, i did consider using a basic lead acid as always turn off the stop/start, but only would save £30.

Not sure about using a charger instead of a slave battery whilst swapping, a smart charger may turn off as not measure any battery resistance.
Using the slave battery I did not have any issues such as resetting windows or warning lights, things I have apparently read on here.

 

[190]

A few months back I disconnected my battery overnight while investigating a discharge. The only apparent effect on the car was I lost my trip mileage on that tank of fuel.

 

[Gazwould]

Not sure about using a charger instead of a slave battery whilst swapping, a smart charger may turn off as not measure any battery resistance.
Using the slave battery I did not have any issues such as resetting windows or warning lights, things I have apparently read on here.

Could always use the auxiliary battery I removed as I've no use for it .

 

[rf065]

Using the slave battery I did not have any issues such as resetting windows or warning lights, things I have apparently read on here.

I've replaced the battery in both my 2016 C Class & 2017 SLC, the only settings I lost were the mirrors folding when locking. On checking the menu, they were still enabled and after a couple of starts they started working again.
Interestingly, they both have AGM batteries and started to degrade after only 4-5 years, despite always switching the start/stop off. My previous CLK was still on it's original battery after 13 years with no problems at all.
Are AGM batteries the real problem? And is resetting only a problem for older vehicles?

 

[Muckypaps]

It would have been interesting to know what that new out of the box AGM was before it was fitted as 12.67 volts is not fully charged even if it did fix the stop start.

Out of the box, my new AGM Varta was 12.6 volts before it was fitted.
The old one just managed to start the car at 11.95 volts.

 

[Dave Richardson]

Thank you for your superb write up & clear photographs. my car is suffering with the same problems & I'd not considered anything less than Varta F21 battery with the cheapest being £150, maybe I'll go down the Exide route

 

[Jibbajabba]

As soon as my e63s shows battery 'partially charged' - Start / Stop will not work ... and that is rare as all it takes for it to go from charged to partially is opening the door once or twice without actually driving

 

[BTB 500]

I mentioned in another thread that a new battery has just fixed the stop/start on our ex-demonstrator 2019 C300. The old battery showed 'partially charged' at all times (even after a 2 hour drive), but there were no symptoms/issues other than stop/start not working. From the service history it looks like it was in storage for 9 months before we bought it, which is presumably what killed the 16 month old battery.

 

[Jibbajabba]

I found that driving isn't always enough and I had to use a trickle charger on my 2020 ...